Question

A schoolteacher is worried that the concentration of dangerous, cancer-causing radon gas in her classroom is greater than the safe level of 7 pCi/L. The school samples the air for 16 days and finds an average concentration of 7.4 pCi/L with a standard deviation of 1 pCi/L. Calculate the value of the test statistic.

a) t₁₅ = −1.60

b) z = −1.60

c) t₁₅ = 1.60

d) z = 1.60

Answer 1

SOLUTION:

this is the RIGHT tailed test .  

The null and alternative hypothesis is ,

H0 :   = 7

Ha : >7

df=n-1=16-1=15

Test statistic = t

= ( - ) / s / n

= (7.4-7) / 1/ 16

= 1.6

t,df=t,15 =1.6

correct option c) t15 = 1.60